In recent years, solid-state image sensors including an optical waveguide for increasing the amount of light that enters a photoelectric converter have been proposed. For example, PTL 1 discloses a method of manufacturing a solid-state image sensor having a groove, from which a part of a photosensitive material (waveguide material) forming as optical waveguide is removed, in a pixel region. PTL 2 discloses a method of manufacturing a solid-state image sensor including a step of flattening a photosensitive material in a pixel region by CMP (Chemical Mechanical Polishing) or the like.